Cast refiner plate segment with blunt edges and corners for safe handling

ABSTRACT

A cast metal plate segment for a refiner of lignocellulosic material or a disperser of comminuted paper or packaging products, the plate segment including a front side with a front surface configured to refine the lignocellulosic material or disperge the comminuted paper or packaging products, and a back side, opposite to the front side, including a corner or edge, wherein the corner or edge comprises a casted surface between machined planar surfaces adjacent the corner or edge.

RELATED APPLICATION

This application claims priority and incorporates by reference U.S.provisional application Ser. No. 61/759,579 filed Feb. 1, 2013.

TECHNICAL FIELD

This disclosure relates to mechanical refiners for pulping wood chipsand other comminuted lignocellulosic materials. The applicationspecifically relates to refiner plates used in mechanical refiners.

BACKGROUND OF THE INVENTION

Mechanical refiners are employed in the production of pulp material fromlignocellulosic material to be used in the making of paper or otherpaper-based packaging material. Mechanical refiners can also be used toproduce pulp from recycled paper material. Mechanical refiners thatprocess recycled material are typically referred to as dispergers ordispersers.

Mechanical refiners may use a flat refining surface, a conical refiningsurface or a combination of flat and conical refining surfaces.Mechanical refiners may comprise two sets of flat discs, a rotatingdisc, commonly known as a “rotor,” and a stationary disc, commonly knownas a “stator.” Some mechanical refiners may use two rotating discs orthe mechanical refiners may use conical-shaped discs configured ineither of the previously described manners. Refiner plates are mountedonto discs, which in turn are mounted in the refiner. A gap existsbetween the discs through which feed material may move. Feed materialmay comprise wood chips or other cellulosic material. The refiningaction occurs as feed material passes generally outwardly through thegaps between the opposing relatively rotating discs.

In a mechanical refiner, the feed material is generally acted upon as itmoves along the surfaces of the refiner plates thereby allowing forseparating and cutting of the material. The refining plate surfaces ofthe opposing discs in a refiner are typically a combination of bars andgrooves facing one-another and crossing each other as at least one ofthe discs moves, or by a series of intermeshing teeth which crossone-another thereby applying compression and shear forces to thematerial to be refined. The refiner plates are generally mounted todiscs and provide the opposing surfaces for refining. The feed materialgenerally moves through the gap formed between the opposing surfaces ofthe plates.

Conventional mechanical refiners are generally capable of handling high,medium, or low consistency feed material, whereas conventionaldispersers are generally capable of handling recycled feed material.Refiner plates, for a conventional mechanical refiner or a disperser area critical component of the refining or dispersing equipment and must becapable of handling the feed material (high, medium, or low consistencyfeed material or recycled or recovered comminuted paper or packagingmaterial used as feed material). The geometries of surfaces of therefiner plates mounted on the discs, such as bars and grooves orintermeshing teeth, typically determine the quality of the work appliedto the feed material to be refined.

As feed material moves across the surface of the refiner plates, thesurface of the refiner plates tend to wear down and become lesseffective in providing the desired refining or dispersing action. Thewearing of the refiner plates encourages regular changing of the refinerplates to maintain the refining or dispersing performance over time. Atypical circle of refiner or disperser plates comprises between 3 and 24equally-sized segments, which together form a circle.

Mechanical refiners, including dispersers, typically have refiner platesmounted to the discs. These refiner plates are typically made insegments. These segments are generally annularly truncated wedges, suchas pie-shaped wedges, but the segments could be other shapes. A seriesof segments may be mounted adjacent to one another on the disc to form acomplete refiner plate.

The “refiner plate segments,” which can describe both mechanical refinerplate segments and disperser refiner plate segments, are usually made ofstainless steel or white iron castings machined to fit together as a setin the refiner. The materials used for these segments are relativelyhard alloys and the castings require precision machining of allsurfaces. This precision machining results in very sharp edges andcorners, posing a safety concern to those handling the segments.

Over the years, persons handling the segments have received numerousinjuries. While these edges and corners can be buffed by hand to reducethe hazard, hand buffing is time-consuming and costly. There is a longfelt need for a less costly, safer machined plate segment.

BRIEF DESCRIPTION OF THE INVENTION

A mechanical refiner plate segment has been conceived that reduces thehazards of sharp edges on the segment. The locations for reducing sharpedges on the refiner plate segments may be at the junction, e.g., edgesand corners, of machined surfaces on the plate segment. For example,machined surfaces typically meet at the four corners on a refiner platesegment, and at the edges of the ribs on the back side of the refinerplate segment. At these junctions of machined surfaces, the precisionmachining of the metal can result in sharp edges and corners.

To overcome the hazard of the sharp edges and corners on plate segments,blunt surfaces at the junctions may be added directly to the castingmold. These blunt surfaces may be chamfers added to the casting mold atportions of the casting mold that would otherwise form an edge or acorner between machined metal surfaces on the refiner plate. Inalternative embodiments, these blunt surfaces at the junctions may berounded sections added to the casting molds at portions of the castingmold that would otherwise form an edge or a corner between machinedmetal surfaces on the refiner plate.

The cast blunt surfaces added directly to the casting mold are widerthan the blunt surfaces on the refining plate remaining after machiningthe surfaces of the refiner plate. The casting mold generally contains apositive mold of the refiner plate segment. Sand or other such suitablematerial is generally then poured into the mold and sealed to create anegative mold of the refiner plate segment. Molten metal is thengenerally poured into the sand mold to form a cast refiner platesegment. The blunt surfaces can form cast blunt surfaces on thejunctions of the corresponding refiner plate segments that are widerthan the these blunt surfaces after they are machined. The cast bluntsurfaces at the junctions may be a cast chamfer surface or a castrounded surface depending on the type of blunt surface used in the mold.In an exemplary embodiment, the cast blunt surfaces at the junctions arecreated by the casting of the refiner plate segment and not by machiningof the refiner plate segment.

In an exemplary embodiment, a refiner plate segment for the productionof pulp by refining lignocellulosic material has been conceivedcomprising a front side having a surface configured to refine thelignocellulosic material; and a back side having a cast blunt surface ata junction between a first cast surface and a second cast surface on theback side, wherein the first cast surface is substantially perpendicularto the second cast surface.

The use of blunt surfaces at the junctions in the casting mold therebycreates a refiner plate segment which can be handled more safely withoutthe high manufacturing costs associated with hand polishing of therefiner plate segments.

When surfaces are machined on a cast plate segment, the cast bluntsurfaces are generally longer than the depth of grind stock machinedaway from adjacent surfaces. That is, when portions of the refiner platesegment are machined during the precision machining step, the cast bluntsurfaces are not completely machined away. This length prevents themachined surfaces on the plate segment from directly contacting othermachined surfaces at outer junctions of the plate segment. These outerjunctions can be perimeter junctions on the back side of the refinerplate surface, perimeter junctions on the front refiner plate surface,and body junctions on the back side of the refiner plate which are notperimeter junctions; the outer junctions are more likely to be directlyhandled by operators.

In one exemplary embodiment, one (1) millimeter (mm) of grind stock isground from the outer surfaces of the cast refiner plate segment.Machining the outer surfaces removes metal and thereby reduces thecertain dimensions of the surfaces, such as their height or width. Themachined surfaces generally include surfaces parallel to a rotationalaxis of the refiner plate segment and surfaces perpendicular to theaxis. The junction, e.g., edge, between a parallel and perpendicularsurface tends to become very sharp as both surfaces are machined.Casting a blunt surface, such as a chamfer, at one or more of thejunctions between these parallel and perpendicular surfaces is effectiveto avoid sharp edged junctions being formed due to machining. However,if the cast blunt surfaces are too small, they will be entirely removedby machining and will not prevent the formation of sharp edges bymachining. The blunt surfaces should be sufficiently wide so that theyare not eliminated by machining of the parallel and perpendicularsurfaces. By having an unground, i.e., not yet machined, cast bluntsurface at a junction that is about 1 mm greater than the depth of themachined surfaces desired to be ground, the final machined parallel andperpendicular surfaces will generally not contact each other to form asharp edge.

The blunt surfaces at the junctions on the casting mold would generallynot be applied to sections of the casting mold that can be used to formthe front refiner plate surface. The front refiner plate surface has aworking function to manipulate (cut, separate, etc.) the material sentto the mechanical refiner. For example, in some refining applications,if the working surface of the refiner plate segment were cast so thatcast blunt surfaces formed at the edges of the refining bars andgrooves, the result would likely negatively affect the performance ofthe working surface of the refiner plate segments.

All or only some of the junctions between surfaces to be machined couldhave cast blunt surfaces, including those on the interior back side ofthe refiner plate segment. For example, the blunt surfaces applied tothe junctions at the outer perimeter of the refiner plate segment areparticularly useful to reduce sharp edges on the plate segment thatcould cut or otherwise harm persons handling the plate segment.

In exemplary embodiments, this cast blunt surface can be on the outerjunctions of the back side of the refiner plate segments and on theperimeter junctions of the front refiner plate surface. In otherexemplary embodiments, the cast blunt surfaces can be on the outerjunctions of the back side of the refiner plate segments, and the firstand second cast surfaces may be surfaces of a rib on the back side ofthe refiner plate segment. In yet another exemplary embodiment, the castblunt surfaces can be on the outer junctions on the back side of therefiner plate, the perimeter junctions of the back side of the refinerplate segment and on the perimeter junctions of the front refiner platesurface. In yet another exemplary embodiment, not all outer junctions onthe back side of the refiner plate segments may have cast bluntsurfaces. While some embodiments may have cast blunt surfaces at alljunctions where machined metal would otherwise directly contact machinedmetal, it is generally desirable to have cast blunt surfaces on theouter junctions on the back side of the refiner plate segment.

In exemplary embodiments, the cast blunt surfaces may be on the outerjunctions. In other embodiments, the cast blunt surfaces may be on abody junction, and the first cast surface is at the perimeter of theplate segment. In yet other embodiments, the cast blunt surfaces may beon body junctios and the first and second cast surfaces may be surfacesof a rib on the back side of the refiner plate segment. In still otherembodiments, the cast blunt surfaces may be on perimeter ribs of therefiner plate segment and the first and second cast surfaces may besurfaces of the perimeter rib.

In embodiments where the cast blunt surface is a cast chamfer surface,the cast chamfer surface may be at an angle of 105 degrees to 165degrees, desirably 120 degrees to 150 degrees, relative to the machinedhorizontal surface of the edge.

In exemplary embodiments where the cast blunt surface is a cast roundedsurface, the cast rounded surface may have a radius prior to grinding of2.5 mm to 15 mm, desirably 3 mm to 5 mm. This cast rounded surface canbe added to prevent the sharp junction formed by precision machining thecast refiner plate segment and can be achieved at locations wheremultiple surfaces are machined, or a single surface is machined, therebyleaving a safer cast blunt surface on outer junctions on the back sideof the refiner plate segment.

In another exemplary embodiment, the cast blunt surfaces may be acombination of cast chamfer surfaces and cast rounded surfaces. Arefiner plate segment has been conceived for the production of pulp byrefining lignocellulosic material, the plate segment comprises a frontrefiner plate surface configured to refine the lignocellulosic material,and a back side having cast blunt surfaces. The cast blunt surfaces maybe cast chamfer surfaces. In another exemplary embodiment, the castblunt surfaces may be cast rounded surfaces. The front refiner platesurface may comprise a combination of bars and grooves, a series ofteeth, or features configured to apply compression and shear forces tothe material to be refined.

In another exemplary embodiment, a disperser plate segment has beenconceived for removing contaminants from recycled or recoveredcomminuted paper or packaging material comprising a front refiner platesurface configured to act on the comminuted material, and a back sidehaving cast blunt surfaces. The cast blunt surfaces may be chamfered orrounded.

A method has been conceived to form a plate segment for a refiner ordisperser comprising casting a metal plate segment, wherein the castmetal plate segment has a diagonal cast surface between a cast topsurface and a cast side surface, machining the cast top surface to forma machined top surface, machining the cast side surface to form amachined side surface, wherein at least a portion of the diagonal castsurface remains separating the machined top surface and the machinedside surface.

In the method, the machined top surface may be orthogonal to themachined side. The machining of the machined top surface and themachined side surface may remove about 1 mm in depth of cast materialfrom the cast top surface. In exemplary embodiments, the cast bluntsurface may have a radius of at least 1.5 times to 2.5 times a depth ofcast material removed during the machining of the cast top surface andthe cast side surface.

The method may further comprise pouring molten metal into a castingmold, wherein the casting mold has blunt surfaces at junctionscomplementary to outer junctions and body junctions on a refiner platesegment.

Another exemplary embodiment of a casted metal plate segment for arefiner of lignocellulosic material or a disperser of comminuted paperor packaging products has been conceived, the plate segment comprising afront refining surface including a front surface configured to refinethe lignocellulosic material or disperge the comminuted paper orpackaging products, and a back side, opposite to the front side,including an corner or edge, wherein the corner or edge comprises acasted surface between machined planar surfaces adjacent the corner oredge.

A casting mold for a refiner plate segment configured to the manufactureof pulp from lignocellulosic material has been conceived comprisingblunt surfaces integrated at junctions complementary to outer junctionsand body junctions on a refiner plate segment, wherein the bluntsurfaces in the casting mold are wider than a to be machined top surfaceand a machined side surface on the refiner plate segment to be formedfrom the casting mold.

In exemplary embodiments of the casting mold for the refiner platesegment, the blunt surfaces may be rounded surfaces, and these roundedsurfaces may have a radius of at least 1.5 times to 2.5 times a depth ofcast material removed during the machining of the cast top surface andcast side surface.

In other exemplary embodiments of the casting mold for the refiner platesegment, the blunt surfaces may be chamfer surfaces, and these chamfersurfaces may have a length of at least 1.5 times to 2.5 times a depth ofcast material removed during the machining of the cast top surface andcast side surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a conventional large rib with flat machined surfaces of arefiner plate segment.

FIG. 2 shows an exemplary large rib with a chamfer surface of a novelrefiner plate segment.

FIG. 3 shows an exemplary large rib with a rounded surface of a refinerplate segment.

FIG. 4 shows an exemplary back side of a refiner plate segment withchamfer surfaces used throughout the back side of the refiner platesegment.

FIG. 4 a shows the detail in the circle shown in FIG. 4 of an exemplaryrefiner plate segment back side where casted chamfer surfaces are usedon the junctions on the back side of the refiner segment.

FIG. 5 depicts an exemplary casting mold for a refiner plate segmenthaving rounded blunt surfaces at potions of the casting mold that canform outer junctions of the back side of the refiner plate segment.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing will be apparent from the following more particulardescription of example embodiments of the disclosure, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, with emphasis instead being placed uponillustrating embodiments of the disclosed device.

It is desirable to provide a refiner or disperser plate segment withcast blunt surfaces, especially the back side of the refiner platesegment, to reduce the hazardous sharp edges and corners created whenthe cast refiner plate segment is precision machined.

FIG. 1 shows a rib 100 with flat machined surfaces, as currentlyproduced when the cast refiner plate segment is precision machined. Therib 100 has bars 111 and grooves 112 at the bottom. These bars 111 andgrooves 112 are found on the working surface of the refiner platesegment. In current refiner plate segments, the underside of the segmentmay have sharp, square edges and corners, wherein the edges and cornersare collectively referred to as junctions. The cast top surface 140(shown by the dotted lines) and the cast side surface 130 (shown by thedotted lines) intersect to form the cast sharp, square edge 151.

Once cast, the refiner plate segment can be precision machined. Duringmachining, approximately 1 mm of material is ground from the castsurfaces to produce flat metal surfaces, such as a machined top surface110 and machined side surface 120. The junctions between intersectingmetal surfaces form sharp machined metal-to-metal junctions. Junction150 is an example of a sharp edged junction formed by the intersectionof machined top surface 110 and machined edge surface 120. These sharpmachined metal-to-metal junctions 150 have been and continue to be thesource of injuries to personnel handling the refiner plate segments.

FIG. 2 shows an exemplary embodiment where the cast blunt surface is acast chamber surface 225. A rib 200 is depicted with a cast chamfersurface 225 along the edge of the rib 200. The rib 200 has bars 211 andgrooves 212 at the bottom. As with the bars 111 and grooves 112 of FIG.1, these bars 211 and grooves 212 can be found on the working surface ofthe refiner plate segment. The cast top surface 240 (shown by the dottedlines), the cast side surface 230 (shown by the dotted lines) and adiagonal cast surface 226 (shown by dotted lines) intersect. Thediagonal cast surface 226 may be sized to be large enough so theprecision machining of the cast refiner plate segment results in a castchamfer surface 225 forming an angle θ with the horizontal cast topsurface 240, the angle θ being between 105 degrees and 165 degrees,desirably 120 degrees to 150 degrees.

Once cast, the refiner plate segment may be precision machined.Approximately 1 mm of material can be ground from the cast top surface240 and the cast side surface 230, to produce a machined top surface 210and a machined side surface 220. The diagonal cast surface 226 is largeenough not to be fully removed by machining the cast top surface 240 andcast side surface 230. After machining, a portion of the diagonal castsurface that remains. The remaining portion of the diagonal cast surfaceis the cast chamfer surface 225. The cast chamfer surface 225 is betweenthe machined top surface 210 and machined side surface 220. Because ofthe cast chamfer surface 225, the precision machining of the machinedtop surface 210 and machined side surface 203 does not form sharp edgesand corners. The cast chamfer surface 225 generally does not cut thehands of persons handling the plate segments.

The precision machining of the rib 200 can be accomplished to allowmultiple cast chamfer surfaces 225. For example, cast chamfer surfacesmay be machined on each side of the rib 200. In an alternativeembodiment, only one cast chamfer surface 225 may be produced on oneside of the rib 200.

FIG. 3 shows an exemplary embodiment in which the cast blunt surface isa cast rounded surface. This figure depicts a rib 300 with a castrounded surface 325 along the rib 300. The rib 300 has bars 311 andgrooves 312 at the bottom. As with the bars 111 and grooves 112 of FIG.1, these bars 311 and grooves 312 can be found on the working surface ofthe refiner plate segment. The cast top surface 340 (shown by the dottedlines), the cast side surface 330 (shown by the dotted lines), and arounded cast surface 326 (shown by dotted lines) intersect. The roundedcast surface 326 is sized to have a radius of curvature sufficientlylong to ensure that the machining of the cast top surface 340 and thecast side surface 330 do not fully remove the rounded cast surface 326.The portion of the rounded cast surface 326 that remains after machiningis the cast rounded surface 325.

During precision machining, approximately 1 mm of material is groundfrom the cast top surface 340 to produce the machined top surface 310and approximately 1 mm of material can be removed from the cast sidesurface 330 to produce the machined side surface 320. Because the castrounded surface 325 is not fully removed by the precision machining,sharp edges and corners are generally not formed by the intersection ofthe machined top surface 310 and the machined side surface 320.

The precision machining of the rib 300 can be accomplished to allowmultiple cast rounded surfaces 325 (on each side of the large rib 300)as shown. In another exemplary embodiment, only one cast rounded surface325 may be produced.

FIG. 4 shows the back side of an exemplary refiner plate segment 400with cast chamfer surfaces 425 used throughout the back side of therefiner plate segment 400. Cast chamfer surfaces 425 can be used on theouter junctions 425a and body junctions 425b of the refiner platesegment back side. Although this exemplary embodiment depicts chamfersurfaces 425 used throughout most ribs 401 on the back side of therefiner plate segment 400, in other embodiments chamfer surfaces 425 maybe used mostly on select ribs 401 such as the perimeter ribs 402.

FIG. 4 a shows the detail x of FIG. 4. FIG. 4 a depicts the back side ofan exemplary refiner plate segment 400. In exemplary embodiments, thecast chamfer surfaces 425 can be between machined surfaces (see 210 and220 of FIG. 2) that are substantially orthogonal to machined surfaces.

FIG. 5 depicts an exemplary casting mold 500 in which blunt surfaces arechamfer blunt surfaces 515. In other exemplary embodiments, the bluntsurfaces may be rounded blunt surfaces. The casting mold may be apositive mold of the final refiner plate segment. Sand or other suchsuitable material is generally poured into the casting mold 500 andsealed to form a sand mold (not pictured) that is a negative mold of therefiner plate segment. Molten metal is generally poured into this moldto create the cast refiner plate segment (see FIG. 4). The chamfer bluntsurfaces 515 are at portions of the casting mold that would otherwiseform a junction between machined metal surfaces on the refiner plate.These junctions may be formed by substantially orthogonal machinedsurfaces (see 210 and 220 of FIG. 2). In other exemplary embodiments,these junctions may be formed by machined surfaces that form acute orobtuse angles relative to adjacent machined surfaces.

While preferred embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustration and not limitation.

What is claimed is:
 1. A cast refiner plate segment for the productionof pulp by refining lignocellulosic material, the cast plate segmentcomprising: a front side having a surface configured to refine thelignocellulosic material; and a back side having a cast blunt surface ata junction between a first cast surface and a second cast surface on theback side, wherein the first cast surface is substantially perpendicularto the second cast surface.
 2. A cast refiner plate segment of claim 1,wherein the cast blunt surface is a cast chamfer surface.
 3. A castrefiner plate segment of claim 2, wherein the cast blunt surface extendthe perimeter of the plate segment and the first cast surface forms theperimeter of the plate.
 4. A cast refiner plate segment of claim 2,wherein the cast blunt surface is on a body junction, and the first andsecond cast surfaces are surfaces of a rib on the back side.
 5. A castrefiner plate segment of claim 1, wherein the cast blunt surface is acast rounded surface.
 6. A cast refiner plate segment of claim 5,wherein the cast blunt surface is on an outer junction and the firstcast surface is at the perimeter of the plate segment.
 7. A cast refinerplate segment of claim 5, wherein the cast blunt surface is on a bodyjunction and the first and second cast surfaces are surfaces of a rib onthe back side.
 8. A cast refiner plate segment of claim 1, wherein thecast blunt surface is at least one of a cast chamfer surface and a castrounded surface.
 9. A cast refiner plate segment of claim 1, wherein thecast blunt surface is on a perimeter rib of the refiner plate segmentand the first and second cast surfaces are surfaces of the perimeterrib.
 10. A method of forming a plate segment for a mechanical refinercomprising: casting a metal plate segment, wherein the cast metal platesegment has a diagonal cast surface between a cast top surface and acast side surface; machining the cast top surface to form a machined topsurface; machining the cast side surface to form a machined sidesurface, wherein at least a portion of the diagonal cast surface remainsafter the machining and separates the machined top surface and themachined side surface.
 11. The method of claim 10, wherein the machinedtop surface is orthogonal to the machined side surface.
 12. The methodof claim 10, wherein the machining of the machined top surface removesabout 1 mm in depth of the cast top surface and about 1 mm in depth ofthe cast side surface.
 13. The method of claim 10, wherein the portionof the diagonal cast surface that remains is a cast blunt surface.
 14. Acasting mold for a refiner plate segment configured to manufacture pulpfrom lignocellulosic material comprising: blunt surfaces, wherein theblunt surfaces are integrated at junctions complementary to outerjunctions on a refiner plate segment, wherein the blunt surfaces in thecasting mold are wider than a to be machined top surface and a machinedside surface on the refiner plate segment to be formed from the castingmold.
 15. The casting mold of claim 14, wherein the blunt surfaces arerounded surfaces.
 16. The casting mold of claim 15, wherein the roundedsurfaces each have a radius of at least 1.5 times to 2.5 times a depthof cast material removed during the machining of the cast top surfaceand cast side surface.
 17. The casting mold of claim 14, wherein theblunt surfaces are chamfer surfaces.
 18. The casting mold of claim 17,wherein the chamfer surfaces each have a length of at least 1.5 times to2.5 times a depth of cast material removed during the machining of thecast top surface and cast side surface.